1. Field of the Invention
The present invention relates to heart valve delivery catheters and methods of delivering and implanting heart valves using delivery catheters. More specifically, the present invention relates to a delivery catheter with an improved distal tip assembly that is non-traumatic to surrounding body tissue during delivery and withdrawal of the catheter and prevents damage to an implanted prosthetic heart valve when the tip assembly is withdrawn through the implanted prosthetic heart valve.
2. Background
Recently, minimally invasive approaches have been developed to facilitate catheter-based implantation of valve prostheses on the beating heart, intending to obviate the need for the use of classical sternotomy and cardiopulmonary bypass. For example, French Patent Application No. 99 14462 illustrates a technique and a device for the ablation of a deficient heart valve by percutaneous route, with a peripheral valvular approach. International Application (PCT) Nos. WO 93/01768 and WO 97/28807, as well as U.S. Pat. No. 5,814,097 to Sterman et al., U.S. Pat. No. 5,370,685 to Stevens, and U.S. Pat. No. 5,545,214 to Stevens illustrate techniques that are not very invasive as well as instruments for implementation of these techniques.
U.S. Pat. No. 3,671,979 to Moulopoulos and U.S. Pat. No. 4,056,854 to Boretos describe catheter-mounted artificial heart valves for implantation in close proximity to a defective heart valve. Both of these prostheses are temporary in nature and require continued connection to the catheter for subsequent repositioning or removal of the valve prosthesis, or for subsequent valve activation.
With regard to the positioning of a replacement heart valve, attaching a valve on a support with a structure in the form of a wire or network of wires, forming a frame, has been proposed. This frame can be contracted radially in such a way that it can be introduced into the body of the patient percutaneously by means of a catheter, and it can be deployed so as to be radially expanded once it is positioned at the desired target site. U.S. Pat. No. 3,657,744 to Ersek discloses a cylindrical, frame-supported, tri-leaflet tissue heart valve that can be delivered through a portion of the vasculature using an elongate tool. The frame is mounted onto the expansion tool prior to delivery to the target location where the frame and valve are expanded into place.
Current techniques for delivering prosthetic heart valves via a catheter include a transapical approach for aortic valve replacement, typically involving the use of an introducer port, i.e., a large-bore overtube, of a trocar. A crimped, framed valve prosthesis reversibly coupled to a delivery catheter is transcatheterally advanced toward the native valve, where it is either forcefully deployed using a balloon catheter, or, alternatively, passively deployed using a self-expandable system. Accurate positioning of the replacement valve in the native annulus is critical to the success of the implantation. Although prior delivery catheter assemblies are sufficient to delivery a prosthetic valve to the native annulus, they do not provide a precise release mechanism for the valve such that error in placing the prosthetic valve in the native annulus is reduced.
The present invention relates to a delivery catheter with an improved distal tip assembly for a heart valve delivery catheter. Delivery catheters according to embodiments of the present invention can include distal tip assemblies with a distal sheath and a proximal sheath, such that the distal portion of a prosthetic valve can be reoriented after partial release without causing trauma to the implantation site. Distal tip assemblies according to embodiments of the present invention can also include mechanisms for preventing damage to the implanted valve during withdrawal of a distal tip assembly through the valve. Delivery catheters according to the present invention can include a handle assembly having two or more rotatable control knobs on the catheter handle. These control knobs allows for accurate manipulation of the distal tip of the catheter. Delivery catheters according to embodiments of the present invention can also allow for further adjustment of the delivery position of a prosthetic valve retained by the distal tip of the catheter after a portion of the prosthetic valve has been exposed to the body channel.